<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var factory = function(){}
        factory.prototype = {
            sellBicycle:function(model){
                var bicycle;
                switch(bicycle){
                    case 'The speedster':
                        bicycle = new speedster()
                        break;
                    case 'The Lowrider':
                        bicycle = new Lowrider();
                        break;
                    case 'The Comfort Cruiser':
                    default:
                        bicycle = new ComfortCruiser();
                }
            }
        }
    </script>
</body>
</html>